I use duel rates on my Prangster, simply because my Futaba 6EXA has the function and I feel I should use it. I use low rates for taking off and the switch to high rates (unless it's less than 10mph, then high rates for take off, but our flying field seldom has less than 10mph!). I basically switch to high rates for the extra throws I get and the exponential. I can pull loops much tighter and roll much quicker, so it's just a lot more responsive . . . . . important when doing snap rolls 50ft off the ground.